1. Field of the Invention
The present invention relates to a display panel such as a liquid crystal display (LCD) panel. Also, the invention relates to a method of producing a display panel.
2. Description of Related Art
In recent years, a display panel such as a liquid crystal display (LCD) panel, an electro-luminescence (EL) display panel and a plasma display panel (PDP) has been widely used instead of CRT.
The display panel has a display layer for performing display. The display layer is held between a pair of substrates, or is carried or held by single substrate. In the liquid crystal display panel, the display layer is a layer (liquid crystal layer) formed of liquid crystal, and is held between a pair of substrates. The substrates are usually formed of glass substrates, but are formed of resin substrates in some cases. The resin substrate is more resistant to breakage than the glass substrate.
In the display panel, transparent electrodes are formed on the opposite sides of the display layer for changing the state of the display layer to perform display. For example, a voltage is applied across the electrodes to change the state of the display layer, so that the display is performed. The electrodes are usually made of ITO.
The electrode on at least one side is usually formed on the substrate provided for holding or carrying the display layer. The electrode on the substrate is usually electrically connected to a drive element (e.g., drive IC) of a drive device, and a control portion of the drive device applies a voltage via the drive element to the electrode for driving the display panel.
The drive element is mounted directly on the substrate of the display panel in some cases, and is directly connected to the electrode on the display panel substrate. Instead of this, a drive substrate carrying a drive element is connected to the display panel substrate in some cases, so that the electrode on the display panel substrate is connected to the drive element on the drive substrate. The drive substrate carrying the drive element may be of a TCP (Tape Carrier Package) type in many cases.
In the display panel, the following problems may arise when the drive element such as drive IC is connected to the electrode on the display panel substrate.
In the case where the drive IC is directly mounted on the substrate of the display panel, breakage such as cracking may occur in the electrode in the operation of connecting a lead of the drive IC to the electrode with an anisotropic conductive adhesive such as ACF while applying a heat and a pressure during the connecting operation. Since ITO, which is often used as the material of the electrode, is fragile, the foregoing breakage is liable to occur in the ITO electrode. In particular, the breakage of the electrode is liable to occur in the structure in which the ITO electrode is formed on the resin substrate, compared with a structure in which the ITO electrode is formed on the glass substrate.
If the electrode is broken, and thereby the electrical connection between the electrode and the drive element is opened, it becomes difficult to drive the display panel for performing the display.
An object of the invention is to provide a display panel having a substrate provided with a transparent electrode, and particularly to provide the display panel in which electrical connection between the electrode and a drive element can be made with high reliability.
Another object of the invention is to provide a method of producing a display panel having a substrate provided with a transparent electrode, which can produce such a display panel that an electrical connection between the electrode and a drive element can be made with high reliability.
The invention provides a display panel including:
a display layer for performing display;
a flexible substrate for holding or carrying the display layer;
a transparent electrode formed on the flexible substrate; and
a metal film formed on the flexible substrate, electrically connected to the transparent electrode and made of a material different from that of the transparent electrode.
Further, the invention provides a method of producing a display panel including:
an electrode forming step of forming a transparent electrode of a predetermined form on a flexible substrate;
a metal film forming step of forming a metal film of a predetermined form on the flexible substrate so that the metal film is electrically connected to the transparent electrode, the metal film being made of a material different from that of the transparent electrode; and
a step of holding or carrying a display layer with the flexible substrate carrying the transparent electrode and the metal film, the display layer being provided for performing display.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.